Carbon Nanotube Speakers Are Flexible, Transparent

Carbon nanotube speakers have been created; by sending an audio-frequency current through a carbon nanotube thin film, it can be made into a superthin high-performance loudspeaker that emits sound in a wide-frequency range. The carbon nanotube speaker functions without any moving parts or heavy magnets. The video below shows a CNT speaker sewn onto a small, waving flag.

KaiLi Jiang and Shoushan Fan, professors at Tsinghua University in Beijing, and their colleagues at Beijing Normal University, drew out a thin film from CTN arrays and, then, tested the thin film for acoustic properties.

Shoushan Fan explains that when the team passed an alternating current through their CNT thin-film speaker, the film quickly switched back and forth between room temperature and 80°C. These swift temperature changes resulted in pressure oscillations in the air next to the thin-film. Fan reports the team found these thermally-induced pressure oscillations responsible for the sound emitted by the thin-film speaker.

He notes that, when fully stretched, the nanotube speaker became transparent, causing the team to envision attaching it to the front of an LCD screen in place of standard speakers. Some of the more “exotic uses” they dreamed up for the speaker, he says, included the possibility stitching it into clothing to create a kind of “singing and speaking jacket.”

CNT flexible speakers could provide the essential ingredient that is missing in talking tape. In his 1998 novel Distraction, Bruce Sterling wrote about how talking tape, one of my favorite pieces of technovelgy, could help construct a building:

Oscar peeled a strip of tape from a yellow spool and wrapped the tape around a cinder block. He swept a hand-scanner over the block, activating the tape...

Update 24-Nov-2008: Ashley found a great precursor to this idea in the works of Keith Laumer. In Diplomat at Arms (1982), his first story featuring the indomitable Retief, we encounter the command microphone:

Retief reached up and adjusted a tiny stud set in the stiff collar of his tunic. He tapped his finger lightly against the cloth. The sound boomed across the arena. A command microphone of the type authorized a Battle Commander was a very effective device...

The Master of the Games stared at him aghast. This was getting out of control. Where the devil had the old man gotten a microphone and a PA system.
(Read more about Laumer's command microphone)

In the context of the story, it is clear that the fabric of the tunic itself is the loudspeaker. End update.